Genesis says that after the flood of Noah, God promised “never again’’ to so wreak destruction on the earth. Try telling that to folks living in the nine states affected by the floods of the Mississippi. “It’s an act of God,’’ one woman told a reporter. But then, hinting at the wonder of this event, she added, “So who should I be angry at?’’ Blaming God opened a gate into a refusal to blame.

In the worst Mississippi flooding at least since the Great Depression, more than three million acres of farmland have been inundated in Alabama, Tennessee, Mississippi, and Louisiana. In many places, water levels have reached all-time records. Tens of thousands of people have been displaced to higher ground, and the Army Corps of Engineers estimates that up to 25,000 homes are being flooded. Dozens of cities and towns have water where it isn’t supposed to be. Across the region, thousands of jobs have been destroyed, along with crops, businesses, and infrastructure. Pollutants are poisoning land on a scale not seen before. The most impoverished states in the nation are being set back even further. And for each statistic in this litany of devastation, there are unnumbered individuals whose lives have been ruined. A slow-motion catastrophe that began weeks ago is far from over.

But flooding has always been a tale with two meanings. Periodic inundations from the Tigris and the Euphrates were key to the fecundity of the Fertile Crescent, and the consequent invention of agriculture. Tracking the ebb and flow of Nile flooding, including a grasp of lunar effects, was key to ancient science. Similar breakthroughs occurred along the Yellow and Yangtze in China. River valleys have been incubators of civilization. If one may speculate that the hard necessity of coping with floods helped ancients develop the defining human characteristic of cooperativeness, it should not be a surprise to discover in the Mississippi agony a modern parable of the common good.

Last week, engineers found it necessary to divert the water in order to spare vulnerable cities, especially Baton Rouge and New Orleans. Spillways were opened, the flood was redirected. But this meant the swamping not only of marshes and farmland, but of populated areas. “Sacrificing towns to save cities,’’ was the way a CNN crawl put it. The procedure was carried out by authorities with calm deliberation, ample warning, and, most impressively, with good will on the part of those most hurt by the strategy. “While we understand the reasoning behind it, it’s still hard to accept,’’ a resident of an inundated river town said. But she added, “It’s a no-brainer when you look at sacrificing our small community to save New Orleans and Baton Rouge. I’m not angry. I’ve resigned myself.’’

Baton Rouge and New Orleans are still under flood warning, with National Weather Service bulletins continually marked “urgent.’’ If, as expected, the cresting river does not overspill the urban floodwalls this week, that boon will have come at someone else’s expense. The broadly positive spirit that greeted the heartbreaking need to put the welfare of many above that of a few represents the opposite of “not in my backyard,’’ the refusal to carry weight for the common good that has become a hallmark of contemporary American life. In the Mississippi valley, thousands of backyards are under water, with assent. What a contrast, say, to the financial elites who have built walls around their prosperity, while flooding downstream markets with torrents of toxic assets. In today’s “I’ve got mine’’ economy, the rising tide lifts only yachts, while sinking everything else. Something different is happening in the heartland.

With its massive system of levees, weirs, locks, and seawalls, the Mississippi is a monument to government management. The crisis of this flood is a further summons to government accountability. With record levels of rainfall and snow melt, human-caused climate change is at issue again. The unintended environmental consequences of flood mitigation and shipping channel enhancement must be addressed. And, most immediately, the good will of the people of “towns sacrificed for cities’’ must be matched by local, state, and federal responses that make whole those many devastated lives. The woman for whom the common good was a no-brainer concluded, “I just hope the government steps up to the plate in a way they didn’t after Katrina.’’

James Carroll, bestselling author of Constantine’s Sword, is a columnist for the Boston Globe and a Distinguished Scholar-in-Residence at Suffolk University in Boston. His newest book, Jerusalem, Jerusalem: How the Ancient City Ignited Our Modern World (Houghton Mifflin Harcourt), has just been published.

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